All these aforementioned words are derived from the Latin root “annus” which means “year”.

Millennium (N):
This word can be split ups as “mille” meaning “thousand” and “annus” meaning “year”. Thus a year that comes after thousand years is a millennium. Some more familiar cognates of the root “milli” are milligram, million (a number obtained by multiplying thousand by thousand).Millennium is also considered as a year of happiness.

Contextual example:
The millennium bug was one of the most exaggerated bugs in the history of computers.

Biennial (adj): taking place every other year, (of a plant) living two years.
“Bi” means “two” (as in biceps, bigamy), so biennial event is something that occurs after two years (NOT twice a year).

Contextual example:
Because of biennial nature of the cultural festival it was one of the most awaited events taking place in the college.

Perennial (Adj): lasting throughout the year.
As we know that “per” means “thru” (as in perturb) and “annus” means “year”. Thus something that is present throughout the year is perennial.

Contextual example:
The presence of perennial rivers is paramount for the development of a civilization.

Annals (N): a historical record of events year by year.
This word is derived from the root “annales” which in turn is derived from “annus”

Contextual example:
Because of his unbeaten 400 runs against an intimidating team such as England, he has bagged a permanent place in the annals of cricket.

The "proper" meaning of biannual is: "occurring twice a year". Some dictionaries give "every two years" as an alternative, but Wiktionary calls the latter meaning "proscribed". The accepted word for "occurring every two years" is biennial.

A rare word that hasn't been mentioned is sesquiannual or sesquiennial (occurring every 1½ years). It seems to be applied mainly to meetings or conferences.

I need help distinguishing bi- and semi-, espcially in reference to weeks and months. I think a biweekly meeting is twice a week, and a semimonthly one is every other month. Nicht Wahr.

And I get equally confused with flowers, annuals and perennials. I think you plant the former every year, but the latter continue to bloom. But I would not at all be surprised to know I had reversed them.

There is a great deal of confusion in this area.bi- means 2 (think bicycle, bipedal)The American Heritage Dictionary Usage Panel says "Bimonthly is rigidly restricted to . . . once in two months, and biweekly to . . . once in two weeks according to 84 per cent of the Usage Panel. The remainder accept the corresponding secondary senses of twice a month and twice a week, which are more properly expressed by semimonthly and semiweekly."

semi- means 1/2 (think semicircle)

The old curmudgeon Fowler says "bi-prefixed to English words of time . . . gives words that have no merits and two faults: they are unsightly hybrids, and they are ambiguous . . . . natural and unambiguous two-hourly and half-hourly, fortnightly and half-weekly . . . [etc.] . . . [can] be used regularly in place of them . . . ."

vaibhavd85, in the first note of this thread minimized the Millennium bug. It was no small concern. Having personal knowledge of the state of software at the time, I feared the worst and prepared a Y2K stash, anticipating the collapse of all data processing. Most code was written in COBOL and FORTRAN and was very poorly documented. Only the concerted efforts of many computer programmers working on a fearful deadline averted a catastrophe. There were millions of lines of computer code in vital computers all over the world that had to be corrected before we could welcome the 21st century.

I have to agree with Philip the Millenium Bug was not an exaggeration, but for the work of so many almost every critical system was fixed. Just because everything goes right does not mean that the hardwork that went into ensuring success was wasted.

I think some discussion of the time lines discussed in the old testament, particularly about every 7 years loan forgiveness, and up through Jubilee would be a good item to comment one. Anyone, just have that fact of the top of their head?

I have a friend who was a corporate lawyer. He felt terrible about it as it offended his sense of right and wrong as a Christian. He went to Seminary preparing to become a pastor. While studying the rules of the seventh year and of Jubilee in the Bible, he was convinced he was still on the wrong track. He returned to law practice as a bankruptcy lawyer!

Perry might want to weigh in on this. While these laws are firmly fixed in the Hebrew Bible, was there ever an actual Jubilee observed in the Biblical sense? I can't recall reading about one in the Bible.